Download Modules08-04to08

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 8
The Cellular Basis of
Reproduction and Inheritance
Modules 8.1 – 8.11
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
8.2 Cells arise only from preexisting cells
The Cell Theory
• 1. All living organisms are composed of one or more
cells. (1958 Virchow)
• 2. Cells are the most basic unit for function and structure
of all organisms.
• 3. All cells come from cells that already exist through cell
division.
Cellular division has several functions:
– Cell division allows an embryo to develop into an adult
– Cell division heals wounds when inflicted
– It also ensures the continuity of life from one generation to
the next through the production of sperm and egg
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
8.3 Prokaryotes reproduce by binary fission
• Prokaryotic cells divide asexually
– These cells possess a single chromosome, containing
genes. There may be additional plasmids in bacteria.
– The chromosome is replicated
– The cell then divides into two cells, a process called
binary fission
Prokaryotic chromosomes
Figure 8.3B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Binary fission of a prokaryotic cell
Plasma
membrane
Prokaryotic
chromosome
Cell wall
Duplication of chromosome
and separation of copies
Continued growth of the cell
and movement of copies
Division into
two cells
Figure 8.3A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Some EUKARYOTIC CELLS can reproduce both
sexually and asexually
• A eukaryotic cell has many
more genes than a prokaryotic
cell. (A bacteria may have
3000 genes while a human
may have 50,000 to 100,000)
– The genes are grouped into
multiple chromosomes,
found in the nucleus.
– To accomplish cell division,
the chromosomes must go
through temporary
alterations in their structure.
Figure 8.4A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Chromosomes are made of a very long DNA
molecule with thousands of genes. The DNA in
one human cell is approximately 2 meters long.
– Individual chromosomes are only visible
during cell division when they become tightly
coiled.
– Chromosomes are packaged as chromatin.
Chromatin is DNA and proteins.
– What is the adaptive advantage of becoming
tightly coiled when the cell divides?
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Before a cell starts
dividing, the
chromosomes are
duplicated. This must
occur so that each
daughter cell gets the
same amount of DNA as
the cell it came from.
Sister chromatids
Centromere
– This process
produces 2 sister
chromatids which
make up one
chromosome.
Figure 8.4B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• When the cell
divides, the sister
chromatids separate
Chromosome
duplication
– Two daughter
cells are produced
– Each has a
complete and
identical set of
chromosomes
Sister
chromatids
Centromere
Chromosome
distribution
to
daughter
cells
Figure 8.4C
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
8.5 The cell cycle multiplies cells
• The cell cycle consists of two major phases:
– Interphase, where chromosomes duplicate
and cell parts
are made
– The mitotic
phase, when
cell division
occurs
Figure 8.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
8.6 Cell division is a continuum of dynamic
changes
• Eukaryotic cell division consists of two stages:
– Mitosis
– Cytokinesis
– Let’s take a closer look.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
INTERPHASE
PROPHASE
Centrosomes
(with centriole pairs)
Early mitotic
spindle
Centrosome
Chromatin
Nucleolus Nuclear
envelope
Plasma
membrane
Chromosome,
consisting of two
sister chromatids
Figure 8.6
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Fragments
of nuclear
envelope
Centrosome
Kinetochore
Spindle
microtubules
METAPHASE
ANAPHASE
Cleavage
furrow
Metaphase
plate
Spindle
TELOPHASE AND CYTOKINESIS
Daughter
chromosomes
Figure 8.6 (continued)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Nuclear
envelope
forming
Nucleolus
forming
8.7 Cytokinesis differs for plant and animal cells
• In animals, cytokinesis
occurs by cleavage
Cleavage
furrow
– This process pinches
the cell apart
Cleavage
furrow
Figure 8.7A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Contracting ring of
microfilaments
Daughter cells
• In plants, a
membranous cell
plate splits the cell in
two
Cell plate
forming
Wall of
parent cell
Cell wall
Figure 8.7B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Vesicles containing
cell wall material
Daughter
nucleus
New cell wall
Cell plate
Daughter
cells
Motor proteins
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Microtubule
• http://www.cytochemistry.net/Cellbiology/microtubule_structure.htm
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
8.8 Anchorage, cell density, and chemical growth
factors affect cell division
• Most animal cells divide only when stimulated,
and others not at all
• In laboratory cultures, most normal cells divide
only when attached to a surface
– They are anchorage dependent.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cells continue dividing until they touch one
another
– This is called density-dependent inhibition
Cells anchor to dish surface and
divide.
When cells have formed a
complete single layer, they stop
dividing (density-dependent
inhibition).
If some cells are scraped away,
the remaining cells divide to fill
the dish with a single layer and
then stop (density-dependent
inhibition).
Figure 8.8A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Growth factors are proteins secreted by cells
that stimulate other cells to divide
After forming a single layer, cells
have stopped dividing.
Providing an additional supply of
growth factors stimulates further
cell division.
Figure 8.8B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
8.9 Growth factors signal the cell cycle control
system
• Proteins within the cell control the cell cycle
– Signals affecting critical checkpoints determine
whether the cell will go through a complete cycle
and divide
G1 checkpoint
Control
system
M checkpoint
G2 checkpoint
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 8.9A
• The binding of growth factors to specific
receptors on the plasma membrane is usually
necessary for cell division
Growth factor
Plasma membrane
Receptor
protein
Relay
proteins
Signal
transduction
pathway
Figure 8.8B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
G1 checkpoint
Cell cycle
control
system
8.10 Connection: Growing out of control, cancer
cells produce malignant tumors
• Cancer cells have abnormal cell cycles
– They divide excessively and can form abnormal
masses called tumors
• Radiation and chemotherapy are effective as
cancer treatments because they interfere with
cell division
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Malignant tumors can invade other tissues and
may kill the organism
Lymph
vessels
Tumor
Glandular
tissue
Metastasis
1
A tumor grows
from a single
cancer cell.
2
Cancer cells invade
neighboring tissue.
Figure 8.10
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
3
Cancer cells spread
through lymph and
blood vessels to other
parts of the body.
8.11 Review of the functions of mitosis: Growth,
cell replacement, and asexual reproduction
• When the cell cycle operates normally, mitotic
cell division functions in:
– Growth (seen here in an onion root)
Figure 8.11A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cell replacement (seen here in skin)
Dead
cells
Epidermis,
the outer
layer of the
skin
Dividing
cells
Dermis
Figure 8.11B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Asexual reproduction (seen here in a hydra)
Figure 8.11C
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings